1.\" 2.\" Copyright (c) 2000 Alfred Perlstein 3.\" 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/share/man/man9/accf_http.9,v 1.1.2.6 2002/07/02 01:03:59 brian Exp $ 27.\" $DragonFly: src/share/man/man9/accf_http.9,v 1.5 2007/10/20 18:13:25 swildner Exp $ 28.\" " 29.Dd November 15, 2000 30.Os 31.Dt ACCF_HTTP 9 32.Sh NAME 33.Nm accf_http 34.Nd "buffer incoming connections until a certain complete HTTP requests arrive" 35.Sh SYNOPSIS 36.Cd options INET 37.Cd options ACCEPT_FILTER_HTTP 38.Li kldload accf_http 39.Sh DESCRIPTION 40This is a filter to be placed on a socket that will be using 41.Fn accept 42to receive incoming HTTP connections. 43.Pp 44It prevents the application from receiving the connected descriptor via 45.Fn accept 46until either a full HTTP/1.0 or HTTP/1.1 HEAD or GET request has 47been buffered by the kernel. 48.Pp 49If something other than a HTTP/1.0 or 50HTTP/1.1 HEAD or GET request is received the kernel will 51allow the application to receive the connection descriptor 52via 53.Fn accept . 54.Pp 55The utility of 56.Nm 57is such that a server will not have to context switch several times 58before performing the initial parsing of the request. 59This effectively reduces the amount of required CPU utilization 60to handle incoming requests by keeping active 61processes in preforking servers such as Apache low 62and reducing the size of the filedescriptor set that needs 63to be managed by interfaces such as 64.Fn select , 65.Fn poll 66or 67.Fn kevent 68based servers. 69.Pp 70The 71.Nm 72kernel option is also a module that can be enabled at runtime via 73.Xr kldload 8 74if the INET option has been compiled into the kernel. 75.Sh EXAMPLES 76Assuming ACCEPT_FILTER_HTTP has been included in the kernel config 77file or the 78.Nm 79module has been loaded, this will enable the http accept filter 80on the socket 81.Fa sok . 82.Bd -literal -offset 0i 83 struct accept_filter_arg afa; 84 85 bzero(&afa, sizeof(afa)); 86 strcpy(afa.af_name, "httpready"); 87 setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa)); 88.Ed 89.Sh SEE ALSO 90.Xr setsockopt 2 , 91.Xr accept_filter 9 92.Sh HISTORY 93The accept filter mechanism and the 94.Nm 95filter were introduced in 96.Fx 4.0 . 97.Sh AUTHORS 98This manual page and the filter were written by 99.An Alfred Perlstein . 100